1. Field of the Invention
The present invention relates to a bearing.
More particularly, the present invention relates to each main bearing of an automotive set.
2. Description of the Prior Art
Internal combustion engines, whether two or four cycler include one or more reciprocating pistons attached to a crankshaft through connecting rods. The crankshaft, in combination with the connecting rods, translates the reciprocal motion of the piston into a rotary power output. The rotary movement of the crankshaft is transmitted directly or through gear means to drive an element, such as the rear wheels of an automobile. The crankshaft is supported by at least a front and a rear main bearing and one or more intermediate main bearings, depending upon the length of the crankshaft, the power output, and other factors. Each of these main bearings must be of relatively close tolerance and well lubricated to withstand the applied forces and minimize friction and wear.
The crankshaft extends through an aperture within the engine wall in proximity to the rear main bearing for attachment to a flywheel or the like. A rear main seal is disposed intermediate the engine wall and the protruding crankshaft to prevent oil seepage therebetween.
In conventional internal combustion engines, an annular space exists intermediate the rear main seal and the rear edge of the rear main bearing. This space, in combination with a return passageway to the oil sump, provides a means for collecting the oil outflow rearwardly from the rear main bearing and returning it to the oil sump. With the almost exclusive present use of full pressure lubricating systems in automobile engines and the high ambient oil pressures, the annular space and associated passageway adjacent the rear main seal is generally inadequate in preventing a high pressure buildup in proximity to the rear main seal. The high pressure buildup in combination with the force of the oil outflowing from the rear main bearing tend to deteriorate and deform the rear main seal, resulting in oil leakage therethrough.
FIG. 1 is a schematic representation of a full pressure lubrication system disposed within an automotive internal combustion engine 1. A crankshaft 2 is mounted within the block of the internal combustion engine 1 by means of front main bearing 3, main bearings 4, 5, and 6 and rear main bearing 7. The crankshaft 2 extends rearwardly of internal combustion engine 1 through a rear main seal 8 and terminates at a radial flange 9. Crankshaft 2 also includes connecting rod bearings 3a, 4a, 5a, and 6a. The front of the crankshaft 2 may include a timing gear 10 and may extend forwardly of the engine to support one or more pulleys 11. The open bottom part of the block is Covered by a downwardly extending pan 12, which pan 12 also serves as an oil sump. A chain or gear driven cam shaft 13 is disposed within the block above the crankshaft 2. The camshaft supports a plurality of push rods, which push rods act through a rocker assembly to open and close the valves. The rocker assembly or assemblies are housed within one or more valve covers 14 and 15.
An oil pump 20, normally housed within pan 12, has an oil pickup disposed within the oil sump. The oil pump pumps the oil through a filter 21 into main oil gallery 22. The main oil gallery feeds oil to each of the main bearings through oil lines 24, 25, 26, 27, and 28. A plurality of passageways are generally disposed within crankshaft 2 to distribute oil from the main bearings to the bearings intermediate the crankshaft 2 and the connecting rods. Additional oil lines 29, 30, 31, and 32 supply oil to the camshaft bearings. A passageway 33 distributes oil to the valve lifter oil gallery 34 and rocker arm oil galleries 35 and 36. Oil return to the oil sump is effected by drainage through various passageways.
Automotive internal combustion engines 1 of a few years ago were designed to operate at low rpm with high torque at low rotational speed. For those internal combustion engines 1 which used full pressure lubrication systems, the oil pump pressure was generally in the vicinity of twenty pounds per square inch and ranged up to thirty pounds per square inch in rare instances. Recent modifications of internal combustion engine ,1 design criteria have caused the internal combustion engines 1 to operate at substantially increased rpm and high tolerances. In order to obtain adequate lubrication under these operating parameters, the oil pressure has been increased to the vicinity of forty pounds per square inch. The increase in oil pressure, while necessary to adequately lubricate the internal combustion engine 1, has created problems in obtaining adequate and long lasting oil seals. One such troublesome seal has been the rear main seal 8.
Referring now to FIG. 2, the operation and elements are described. The underlying support for the rear main bearing of crankshaft 2 is provided by a cylindrical depression 40 disposed within the corresponding part of block 41 of internal combustion engine 1. A bearing cap 42, having a mating semi-cylindrical depression 43, is bolted to block 41, to retain the crankshaft 2 and rear main bearing 7 therebetween. A pair of mating radially flanged semi-cylindrical bearings 44 and 45 are seated within depressions 40 and 43, respectively, with the radial flanges preventing axial or longitudinal displacement of the bearings.
The rear main seal 8 is retained within a mating circular aperture 47, disposed within the rear wall of internal combustion engine 1 to encircle the protruding part of crankshaft 2. As mentioned above, the purpose of the rear main seal 8 is that of preventing oil flow adjacent the surface of the protruding part of the crankshaft 2.
An annular cavity 48 is disposed about crankshaft 2 intermediate the rear radial flanges of bearings 45 and 46 and the rear main seal 8. A passageway 49 interconnects the annular cavity with the oil sump to permit oil drainage into the sump from the annular cavity. Oil pan 12 is bolted or otherwise secured to the lower surface of block 41 with an intermediate seal 50.
Normally, lubrication for the rear main bearing is provided by oil flow through oil line 24 within block 41, which oil line terminates coincident with an aperture 53 extending through bearing 44. A slot 54 is disposed within the inner surface 55 of bearing 44 to distribute the oil inflowing through slot 53 intermediate the bearing and the bearing surface of crankshaft 2. By well known hydraulic principles, the oil disposed within slot 54 will be distributed intermediate the inner surfaces of both bearings 44 and 45 and the corresponding bearing surfaces of crankshaft 2. The normal oil outflow from bearings 44 and 45 will be forwardly and rearwardly along the crankshaft 2. The oil flowing forwardly will ultimately drip into the oil sump. The oil flowing rearwardly, will tend to strike rear main seal 8 and collect within annular cavity 48 with drainage therefrom occurring through passageway 49.
As shown in FIGS. 2, 3, and 4, in earlier internal combustion engines 1 having oil pressures in the range of twenty pounds per square inch, the force of the oil outflowing rearwardly from the rear main bearing 7 had a low velocity and was low in volume. However, when the oil pressure was increased to forty pounds per square inch without redesigning the lubrication system in proximity to the rear main bearing 7, the outflowing oil acquired sufficient force to damage and cause deterioration of rear main seal 8. Moreover, the increased volumetric flow exceeded the oil collection and discharge capability of the annular cavity 48. Hence, a high pressure environment was created within the annular cavity and placed a strain upon the rear main seal 8.
By forming one or more forwardly extending shallow depressions or channels 60 and 61 in inner surface 56 of lower bearing 45, passageways are established to induce forward flow of oil from the lower bearing 45. The forward flow of the oil relieves the pressure buildup within annular cavity 48 and reduces both the volume and velocity of the rearwardly flowing oil. In internal combustion engines 1 where the forward surface 57 of flange 58 abuts a planar surface of crankshaft 2, a relief must be provided to permit oil flow therebetween. Such a relief is accommodated by means of a pair of radially extending depressions 62 and 63.
It may also be pointed out that by limiting the length of channels 60 and 61, such that they extend inwardly (longitudinally) from the forward edge of the bearing surface to a point short of the rear edge of the bearing surface, no reduction in lubrication or the quality thereof has been experienced. The number of channels and their orientation may, of course, vary depending upon the ambient oil pressure, the viscosity of the oil and the bearing tolerances. However, it has been learned that for most popular cars manufactured in America, two channels disposed in opposite sides of the lower bearing and extending across approximately four-fifths of the bearing surface and angled toward the low point of the bearing surface has produced very satisfactory results. Moreover, the width of the channels may be on the order of 1/8 of an inch and their depth may range from one thousands to ten thousands of an inch. The exact and preferred dimensions will vary with the type and nature of the bearing in conjunction with the nature of the existing lubrication system.
It may be noted that the annular depressions 65 and 65' are a function of the bearing design and do not form a part of the bearing surfaces (54, 56).
After an internal combustion engine 1 without modified rear main bearings has been shut off, there may exist a pressure buildup within the oil distribution system for varying periods of time, dependent to a great extent upon the amount of sludge in the oil, constrictions within return passages and the tolerance between the parts wherethrough the oil must flow. At the rear main bearing 7, it is not unusual to have a substantial pressure buildup intermediate the rear main bearing 7 and the corresponding bearing surface of the crankshaft 2 and within the annular cavity for a substantial period after the oil pump has ceased to operate. The slowly decaying pressure environment tends to cause oil seepage intermediate the rear main seal 8 and the crankshaft 2. In many cases, this pressure environment is responsible for the oil drips which occur after a car is parked.
If channels 60 and 61 are employed, there will occur an almost immediate complete pressure relief within the rear main bearing 7 after the internal combustion engine 1 is shut off. Hence, there is only a short period lingering pressure environment within the rear main bearing and the adjacent annular cavity.
Numerous innovations for automotive rear main bearings have been provided in the prior art that are adapted to be used. Even though these innovations may be suitable for the specific individual purposes to which they address, they would not be suitable for the purposes of the present invention as heretofore described.